Conventionally, an analog to digital converter (ADC) is provided for converting an analog signal to a digital signal in various types of electronic devices such as a camera, an audio device, and a measuring device. There are various types of ADCs, but a successive-approximation type ADC is widely used especially because of its small power consumption and circuit scale.
A comparator, a logic circuit, a digital to analog converter (DAC) and the like are provided in the above-described successive-approximation type ADC (for example, refer to Non-Patent Document 1). In the successive-approximation type ADC, the comparator compares input voltage Vin to be converted with reference voltage VDAC from the DAC. The logic circuit controls the DAC on the basis of a comparison result and increases or decreases the reference voltage VDAC. Comparison by the comparator and adjustment of the reference voltage by the DAC are executed alternately by the same number of times as resolution of the ADC.